Process of making indigo from indol.



b of philosophy and chemist, a subject of the PAUL SEIDEL, on LUDWIGSHAFEMGERMANY, ASSIGNOR fro BA IscHE ANILIN & SODA FABRIK, OF LUDWIGSHAFEN, GERMANY, A CORPO- RATION.

PROCESS OF MAKING INDIGO FROM INDOL.

SPECIFICATION forming part of Letters Patent No. 698,328, dated April 22, 1 902. v

Application filed September 24,1901. Serial No, 76,430. (No specimens.)

T0 ctZl whom it may concern:

Be it known that L'PAUL SEIDEL, doctor King of Saxony, residing at 'Ludwigshafenon-the-Rhine, in the Kingdom of Bavaria,

Germany, have invented new and useful Improvementsin'theManufactnre oflndigo from Indol,of which the following-is a specification.

Many attempts have been made to obtain richte, volume 32, page 3625, and also called sulfo-mono-peracid by Baeyer in Berz'chte,

volume 33, page 2480,) which can be obtained from potassium persulfate and concentrated sulfuric acid, as described by Caro in Zeitsohmfifdr Angewandte Ohemie for 1898,p'age 84:5, 01' from hydrogen peroxidand sulfuric acid, as described by Baeyer in Bem'chte, volume 33, page 124. I have also, discovered that oxygen which has been rendered active by such means as sulfite of soda or of bisul-- fite of soda (Wicke in Zeitschriftfltr O'hemze for 1865, pages 80and 305; Jorissenin Zeitschriftfilr Physilcalische O'hemie, volu me 23,

page 667) is an equivalent for converting indol into indigo.

The following examples will serve to further illustrate the nature of my invention and the manner in which the same may be carried into practical effect; but the invention is not confined to the examples; The parts are by weight.

Example 1: Grind together five 3) parts of indol and twenty parts of water to-a fine paste and add to this a solution of Caros reagent, obtained from twenty-five parts of potassium persulfate and twenty-eight (28) parts of concentrated sulfuric acid, (containing about ninety-five per cent; of H SO ,)'di- ATE luted by the addition of one thousand 1,000

parts of ice.

The solution at once turns yelwhich separates out by boiling with anchor;

A red coloring-matter,'so1uble in alcohol, solves and pure indigo remains.

Example 2: Take Caros reagent, obtained as stated in the foregoing Example 1,and neu'-' tralize it by adding an aqueous solution" of forty parts of calcined soda. Add this solutiontoa solutionof ten (10)'pa rts of indol in five thousand (5,000) parts of water and add also sufficient'dilute caustic-soda solution to give the liquid an alkaline reaction. j After a short time the indigo separates out. f

Example 3: Dissolveaboutfive (5)" parts of indol in three thousand (3,000) partsvof Water and add to the solution ten (10)- parts of sodium sulfite dissolved in'fifty ()parts of Water. On standing in the air the s'olution a 17 uid. Add an alkali-t0 theliquid and-allow it to stand exposed to the air'or-blo'w air through the liquid,when the indigo'pro'duced separates on t. c

Example 4:: Dissolve abo'utfive (5) parts of indol in three thousand'(3,'000) partsof'wa-' ter and to the solution add fifty(50)"parts of commercial sodium-bisulfitesolution, (containing about forty per cent. of realbisulfitei) parts of commercial sodium-bisulfite solution (containing about forty per cent; of real bisulfite) and five hundred (500) parts of water and treat the mixture with air, when indigoseparates out. Add caustic soda until the Allow thesolution to standexposed to the-18o "air or blow through it. Indigo begins to sepa- Add caustic soda'to the solution reaction is alkaline and again pass air into In testimony whereof I have hereunto set the mixture, when a further quantity of inmy hand in the presence of two subscribing digo is obtained. witnesses.

Now what I claim is PAUL SEIDEL. 5 The process of man ufacturing indigo which WVitnesses:

consists in treating indol with sulfo-mono- JOHN L. HEINKE,

peracid. JACOB ADRIAN. 

